This invention relates to blocks used for constructing a breakwater which can effectively decrease the force of high magnitude waves while maintaining the stability of the structure thereof.
Conventional breakwaters such as caissons are equipped with no provisions for decreasing the wave force. Therefore, the structure which receives all of the wave force inevitably must be extremely large.
Caissons provided with openings have been proposed and developed for replacing such solid caissons. However, these remodelled caissons also have the following problems in view of their construction and installation and therefore few of them have been installed commercially up to this date.
(a) Since such a caisson has holes, the carrier cannot tow the caisson from the manufacturing site to the installation site. Accordingly, the installation operation requires a large-sized carrier vessel equipped with a gigantic crane, which results in expensive installation. Such a disadvantage is especially remarkable in a small-scale installation operation. PA1 (b) Since the caisson which has openings cannot accommodate the packing or charging material, such a caisson is light in weight although the volume thereof is large. Therefore, this caisson lacks resistance against outer forces such as waves or earth pressures. PA1 (c) Standardization of the caissons corresponding to the size of the installation operation is impossible. PA1 (d) Since the caisson is in general large-sized, the manufacturing facilities also must be large in scale. The operation of such facilities is costly.
Accordingly, in recent times, a method to construct breakwaters with blocks has been proposed. In fact, more than 200 breakwaters have been constructed or installed by the above method. However, with regard to the conventional blocks, when they are stacked one on another, they resist the outer force (such as the wave force) only with the weight of the blocks and the frictional resistance between the contact surfaces of the blocks. Therefore, the breakwater structure constructed with such blocks still has problems to be solved in view of its stability.
It is an object of the present invention to provide blocks which can resolve such defects of conventional blocks while fully utilizing the inherent advantages (readiness of installation, handiness, full running of molds).
It is another object of the present invention to provide such blocks, which, when stacked up, can remarkably increase the stability of the structure.